Sorry to be bearer of bad news, GMAIL has limits on
a) total message size
b) individual attachment size
c) total number of attachments
Apparently, these can be bypassed if the attachments are stored in google drive and the attachments are merely links to the google drive storage though I
a) don't use any cloud storage for business confidential files
b) know how to attach such links
If you really require to beat the default limits you need to read up on these limits and bypasses in places like
Send attachments with your Gmail message - Computer - Gmail Help[
^]
Sorry, I only just noticed the age of this. Way tooooo late :-)